Field of the Invention
The present invention relates to orthopedic implant technology and, more specifically, to surface treatment of endoprosthetic devices that allows for soft tissue attachment thereto.
Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In human patients, disease or extreme trauma can sometimes necessitate the repair or replacement of a portion or all of the bones and/or joints that comprise a patient's arm or leg. For example, a tumor that affects the proximal portion of a patient's humerus can require resection of the diseased portion and fixation of a humeral prosthesis that attempts to duplicate the functionality of the original humerus. Such an endoprosthetic device may typically include the humeral head, shaft, and even the elbow joint, with affixation at the distal end via a shaft feature that is cemented into a borehole formed within the remaining ulna or radial bone of the patient. While such extreme limb-salvage surgical repairs are made nowadays on a somewhat routine basis, existing prosthetic device technology falls short with regard to duplication of the range of movement of the original joints. Consequently, patients are typically left with limited functionality of the replaced anatomy due to limited range of motion. Moreover, patients with such repairs, who attempt arm movements to the limits of these prosthetic devices often weaken or damage the affixation site and may even cause dislocation of the shoulder joint, resulting in additional trauma to the bone and surrounding soft tissue.
The instant inventor made tremendous advances in orthopedic implant technology with his invention disclosed in PCT Application No. PCT/US2011/056393 entitled “Modular Humeral Prosthesis With Spherocentric Feature,” filed on Oct. 14, 2011, the disclosure of which is incorporated by reference herein for all purposes. As the title states, this invention discloses a modular humeral prosthesis having a new and unique spherocentric elbow joint that allows full supination and pronation of the patient's hand post-recovery. However, as with this and other current humeral prostheses it was discovered that upon repeated medial and lateral rotation of the patient's repaired arm excessive torsional stresses were imparted on the humeral prosthesis shaft. In the case of complete shoulder repairs the excessive torsional stresses resulted in full separation and dislocation of the shoulder joint with resultant damage to the joint and surrounding soft tissue. In the case of partial humerus repair the excessive torsional stresses resulted in “windshield wiper” loosening of the cemented stem from the fixation site.
In addition, successful attachment and integration of soft tissue to this and other endoprosthetic devices has been elusive. To reattach a forcefully contracting muscle to an inert endoprosthesis has currently required use of an artificial tendon or other point-type anchoring device. Such artificial tendons and anchoring devices do not afford optimal integration of the tendon to the prosthesis, which would spread the forces of muscle contraction over a greater area for optimal strength. Instead, the forces are concentrated in the artificial anchoring device, resulting in a weaker interface that causes patient discomfort or pain if the muscle separates completely from the anchor. What is needed is an endoprosthetic surface treatment and method for soft tissue attachment thereto that affords integration similar to the normal tendo-osseous junction. The instant invention addresses these shortcomings and others as will be understood by one of ordinary skill upon a thorough study of the embodiments described herein.